1. Field of the Invention
The present invention relates to a process for producing a TiB.sub.2 -dispersed TiAl-based composite material. More specifically, TiB.sub.2 is uniformely dispersed in TiAl intermetallic compound-based matrix.
2. Description of the Related Art
The TiAl intermetallic compound is promising as a light-weight high temperature structural material since it has both metallic and ceramic properties, has a low density and has an excellent high temperature specific strength. The TiAl intermetallic compound is however limited in its applications since its hardness is low in comparison with normal metals and alloys.
To improve the hardness of the TiAl intermetallic compound, a TiAl-based composite material in which TiB.sub.2 is dispersed was developed. For example, JP-A-03-193842, published in August, 1991, discloses a process for producing such a composite material, said process compressing mixing and melting powders of Al matrix containing TiB.sub.2 dispersed therein, Al metal powders and Ti metal powders, followed by solidifying the same to form a TiAl intermetallic compound in which TiB.sub.2 particles are dispersed.
As TiB.sub.2 particles are dispersed in TiAl intermetallic compound, generally, the hardness of the TiAl intermetallic compound increases but the ductility thereof decreases. It is therefore necessary that TiB.sub.2 particles are finely dispersed in the TiAl intermetallic compound. When the composite material is deformed, the matrix is deformed with cracks being formed. If the TiB.sub.2 particles dispersed in the matrix are large, cracks are interrupted by the TiB.sub.2 particles and the matrix cannot be deformed and is split or broken. In contrast, if the TiB.sub.2 particles dispersed in the matrix are fine, cracks may develop through the gaps between the TiB.sub.2 particles and the matrix can be deformed. Accordingly, it is considered that reduction of ductility of the matrix can be suppressed by finely dispersing TiB.sub.2 particles in the matrix.
In the above mentioned process of producing a TiB.sub.2 -dispersed TiAl intermetallic compound-based composite material, however, it is difficult to finely disperse TiB.sub.2 in a TiAl intermetallic compound since TiB.sub.2 particles agglomerate with each other when the mixture of the TiB.sub.2 -dispersed Al powders, Al metallic powders and Ti metallic powders are melted.
The purpose of the present invention is to provide a process for producing a TiB.sub.2 -dispersed TiAl intermetallic compound-based composite material in which the dispersed TiB.sub.2 is fine so that the reduction of the ductility of the material is suppressed while the hardness of the material is increased.